Dynamic stall control by oscillatory forcing

A parametric study was undertaken to investigate the effect of oscillatory forcing (with zero net mass-flux) on an airfoil undergoing pitch oscillations at rotorcraft reduced frequencies. The primary objective of the study was to maximize the airfoil performance while simultaneously limiting moment excursions to typical pre-stalled conditions. The incidence angle excursions were limited to ±5° and a wide range reduced forcing frequencies and amplitudes were considered for /?e<0.3xl0 with various flap deflections and forcing locations. Significant increases in maximum lift and reductions in form drag were attained while simultaneously containing the moment excursions. Oscillatory forcing was found to be far superior to steady blowing and flap-shoulder forcing was found to be superior to leading-edge forcing.